Washing bottles

do you wash (with soap and water) your babies bottles after every single use or is rinsing with hot water to refill a second time okay ?

Example :

my son eats 3 ounce at 10am - falls asleep so

I rinse out the bottle with hot water and put it to the side ... he wakes up at 11am and he wants more food, can I just use the bottle I just rinsed out for another 1-2 ounces and then just wash it after that?

Or should I wash it with soap and water after every single feed ?